Generally, a content providing server encodes contents in a predetermined encoding method and transmits the encoded contents to content consuming terminals that consume the contents. The content consuming terminals decode the contents in a predetermined decoding method and output the transmitted contents.
Accordingly, the content providing server includes an encoding unit for encoding the contents and a transmission unit for transmitting the encoded contents. On the other hand, the content consuming terminals includes a reception unit for receiving the transmitted encoded contents, a decoding unit for decoding the encoded contents, and an output unit for outputting the decoded contents to users.
Many encoding/decoding methods of audio/video signals are known so far. Among them, an encoding/decoding method based on Moving Picture Experts Group 4 (MPEG-4) is widely used these days. MPEG-4 is a technical standard for data compression and restoration technology defined by the MPEG to transmit moving pictures at a low transmission rate.
According to MPEG-4, an object of an arbitrary shape can be encoded and the content consuming terminals consume a scene composed of a plurality of objects. Therefore, MPEG-4 defines Audio Binary Format for Scene (Audio BIFS) with a scene description language for designating a sound object expression method and the characteristics thereof.
Meanwhile, along with the development in video, users want to consume contents of more lifelike sounds and video quality. In the MPEG-4 AudioBIFS, an AudioFX node and a DirectiveSound node are used to express spatiality of a three-dimensional audio scene. In these nodes, modeling of sound source is usually depended on point-source. Point-source can be described and embodied in a three-dimensional sound space easily.
Actual point-sources, however, tend to have a dimension more than two, rather than to be a point of literal meaning. More important thing here is that the shape of the sound source can be recognized by human beings, which is disclosed by J. Baluert, “Spatial Hearing,” the MIT Press, Cambridge Mass., 1996.
For example, a sound of waves dashing against the coastline stretched in a straight line can be recognized as a linear sound source instead of a point sound source. To improve the sense of the real of the three-dimensional audio scene by using the AudioBIFS, the size and shape of the sound source should be expressed. Otherwise, the sense of the real of a sound object in the three-dimensional audio scene would be damaged seriously.
That is, the spatiality of a sound source could be described to endow a three-dimensional audio scene with a sound source which is of more than one-dimensional.